Dual flush device for toilets

ABSTRACT

A dual flush device comprises a mounting structure and a float to retrofit single flush toilets to dual flush toilets. The mounting structure is attached to an overflow tube and connected to the float with a vertical bar along which the float can move vertically downward or upward with the water level in the toilet tank. The float includes a water-tight container and a bottom part screwed into the bottom of the container. The vertical length of the float is adjustable by rotating the bottom part either away or toward the container. Several embodiments of the mounting structure and float are invented to accommodate various toilet models. The dual flush device operates with a flapper valve and a single flush handle assembly and maintains the modular design of conventional toilets. The float will prematurely close the flapper valve in a partial flush using less water than in a full flush.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application claims the benefit of and priority to U.S. Provisional Patent Application No. 62/270,161, which was filed on Dec. 21, 2015. The foregoing U.S. provisional patent application is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

The conventional single flush toilets lack a partial flush for removing liquid wastes using significantly less volume of water than in a full flush. On average, four out of every five toilet flushes, or 80 percent of the flushes, are for removing liquid wastes. Adding a partial flush option to these toilets would therefore benefit the user by reducing water and sewer costs for 80 percent of the toilet flushes. Many dual flush devices or mechanisms have been invented to provide the user with the partial flush and the full flush, and they are described in a number of the prior art patents on this topic. For example, about 140 U.S. patents among them are referenced in U.S. Pat. No. 7,591,027. A comprehensive, state-of-the-art review of many dual flush devices of the prior art is presented in U.S. Pat. No. 8,584,268. However, many prior art devices would be likely to be relatively expensive to manufacture due to complex designs (e.g., using a dual flush handle assembly with two concentric shafts and two flush levers), difficult to install (e.g., requiring the removal of the toilet tank), expensive to repair a leaking flush valve (due to replacing the flapper valve with a new flush valve assembled in a unit or package with other parts), and/or unreliable to operate (due to complex designs with too many moving parts).

Advantages of the dual flush device of the present invention over a number of the devices disclosed in the prior art include: (1) providing a simple design with only one moving part (e.g., a float to be later discussed) to reduce cost and enhance reliability; (2) providing an easy installation without toilet tank removal; (3) maintaining the modular design of the conventional toilets to keep the inherent convenience and economy of maintenance and part replacement (e.g., replacing a leaking flapper valve) by being installed as a separate module in operation with the conventional single flush handle assembly and the flapper valve; and (4) providing an adjustable partial flush that allows the user to increase the volume of water used in the flush to produce a wide range of flushing power from removing liquid wastes to removing a fair load of solid wastes, for accommodating differences in the conventional toilets in tank sizes, water levels, flushing hydrodynamics, and drain line conditions.

SUMMARY OF THE INVENTION

The present invention describes a toilet dual flush device that comprises a mounting structure and a float, configured to attach and fasten to the overflow tube in a toilet tank. The float is loosely connected to the mounting structure by inserting with a vertical bar of the mounting structure, and its function is to prematurely close the flapper valve by moving vertically downward with the falling water level in the tank during the partial flush. The mounting structure has an upper horizontal extension and a lower horizontal extension to respectively limit the upper and lower movements of the float. The mounting structure also has an L-shaped vertical block configured to engage a vertical channel on the float to help maintain the vertical movement of the float along the vertical bar in the flush. The vertical length of the float is adjustable by inserting a bottom part, formed by a vertical threaded rod integrally attached to a horizontally elongate bottom head, into a vertical threaded hole in a container of the float. For instance, the vertical length of the float is increased by rotating the bottom part away from the container of the float, and it is decreased by rotating the bottom part toward the float container. Physically, increasing the vertical length of the float will generally use less volume of water in the partial flush by closing the flapper valve earlier, while decreasing the vertical length of the float will generally use more volume of water in the partial flush by closing the flapper valve later. An important point to make is that the length-adjustable float enables the user to preselect the volume of water to use in the partial flush to produce the flushing power in a wide range from removing liquid wastes to removing a fair load of solid wastes from the toilet. Several embodiments of the mounting structure are introduced to provide various configurations for attaching and fastening the mounting structure to the overflow tube. A few embodiments of the bottom part of the float are also introduced for making a good contact with the flapper valve in the partial flush, after connecting the float to the mounting structure attached and fastened to the overflow tube at a proper axial and horizontal location above the flapper valve.

The dual flush device works with the single flush handle assembly and the flapper valve in a conventional toilet to provide the user with the adjustable partial flush and the full flush. The partial flush is activated by depressing the flush handle to open the flapper valve to allow the float to move vertically downward along the vertical bar and the L-shaped vertical block of the mounting structure with falling water level to prematurely close the flapper valve. During tank refill, the float will move vertically upward along the vertical bar and the L-shaped vertical block of the mounting structure with rising water level until reaching a normal pre-flush level. The full flush is activated by briefly holding down the flush handle to keep the float in place during tank draining.

BRIEF DESCRIPTION OF THE DRAWINGS

Twenty-nine drawings are provided to show various embodiments and views of the dual flush device of the present invention, not necessarily drawn to scale.

FIG. 1 is a front elevation view of a toilet tank showing an embodiment of the dual flush device, attached and fastened to the overflow tube in a conventional toilet.

FIG. 2 is a perspective view of a first embodiment of the mounting structure but with the vertical bar removed (comparing to FIG. 12 that shows the entire first embodiment of the mounting structure including the installed vertical bar).

FIG. 3 is a section view of the mounting structure at a cutting plane line A-A in FIG. 2, showing a double-wall cylindrical structure at the upper section and a single cylindrical wall at the lower section.

FIG. 4 is a limited top view of FIG. 2 showing only the outer cylindrical wall boundary of the mounting structure with the upper horizontal extension in the upper figure and with the lower horizontal extension in the lower figure.

FIG. 5 is a section view of the mounting structure at a cutting plane line B-B in FIG. 2 (also in FIGS. 13-14 and 17).

FIG. 6 is a top view showing only the upper section of the mounting structure in FIG. 2.

FIG. 7 is a limited side elevation view showing only a refill tube holder on top of the mounting structure in FIG. 2.

FIG. 8 is a perspective view of an embodiment of the vertical bar, installed in several embodiments of the mounting structure in FIGS. 12-14,16-17, and 20.

FIG. 9 is a section view of a top head of the vertical bar at a cutting plane line C-C in FIG. 8.

FIG. 10 is a section view of a short upper section of the vertical bar at a cutting plane line D-D in FIG. 8.

FIG. 11 is a section view of a vertical body of the vertical bar at a cutting plane line E-E in FIG. 8.

FIG. 12 is a perspective view of the first embodiment of the mounting structure.

FIG. 13 is a perspective view of a second embodiment of the mounting structure.

FIG. 14 is a perspective view of a third embodiment of the mounting structure.

FIG. 15 is a section view of the third embodiment of the mounting structure at a cutting plane line A-A in FIG. 14, showing a hollow cylindrical wall.

FIG. 16 is a front elevation view of a toilet tank showing the third embodiment of the mounting structure attached and fastened to the overflow tube.

FIG. 17 is a perspective view of a fourth embodiment of the mounting structure.

FIG. 18 is a section view of the fourth embodiment of the mounting structure at a cutting plane line A-A in FIG. 17, showing a single-wall cylindrical structure with a cylindrical wall integrally attached at the top to a ring-shaped horizontal wall that has the same outside diameter but a smaller inside diameter than the cylindrical wall.

FIG. 19 is a perspective view of an adapter for attaching and fastening a fifth embodiment of the mounting structure in FIG. 20 to the overflow tube.

FIG. 20 is a perspective view of the fifth embodiment of the mounting structure for engaging the adapter in FIG. 19.

FIG. 21 is a section view of the fifth embodiment of the mounting structure along a cutting plane line F-F in FIG. 20.

FIG. 22 is a perspective view of an embodiment of the float.

FIG. 23 is a perspective view of the float in FIG. 22 with the intentional removal of a top cover and a bottom part.

FIG. 24 is a top view of the portion of the float in FIG. 23.

FIG. 25 is a bottom view of the portion of the float in FIG. 23.

FIG. 26 is a perspective view of an embodiment of the bottom part of the float in FIG. 22.

FIG. 27 is a top view of the bottom part of the float in FIG. 26.

FIG. 28 is a perspective view of another embodiment of the bottom part of the float (to optionally replace the one shown in FIG. 22).

FIG. 29 is a top view of the bottom part of the float in FIG. 28.

For clarity, same part numbers are used in the drawings to identify similar parts in various embodiments (e.g., part numbers 6,10-13, and 15-17 in FIGS. 2,13, 14, and 17), and similar part numbers with some variations are used to identify partially similar parts (e.g., part numbers 10, 15, and 16 in FIG. 2, compared respectively to part numbers 10D, 15D, and 16D in FIG. 20).

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a dual flush device 1 installed in a toilet tank 49, comprising a mounting structure 2 (e.g., the first embodiment of the mounting structure) and a float 3 including a vertical bar 4 and a bottom part 5. Mounting structure 2 is attached to or mounted on a top section of an overflow tube 36 and fastened to it with a hand-tightening nut 6, which is installed in a protruding section 11 on mounting structure 2. A notch 7 and a refill tube holder 8 are on mounting structure 2, and an external vertical channel 27 with an inner wall 28 and an outer wall 29 is part of float 3. Float 3 is shown at an approximately normal pre-flush position at the moment when the user has just depressed a flush handle 47 to open flapper valve 37, which will fall with a falling tank water level 51 in the partial flush. Other parts in FIG. 1 include mounting posts or lugs 40 on overflow tube 36 where flapper valve 37 is pivotally mounted, a flush valve seat 43, a discharge pipe 44, a flush handle knob 48 mounted through a built-in hole on a tank wall 50 and firmly connected to a flush or tank lever 45 having multiple holes 46, a hook 42 linking flush lever 45 via one of holes 46 to a chain 41 that connects at other end to flapper valve 37 at an eyelet 39 located outward from a top surface 38 of flapper valve 37. A conventional toilet tank also has a fill valve or inlet valve controlling water flow into the tank, which is purposely omitted inside tank 49 to provide space to focus on dual flush device 1 and its operation with flapper valve 37 and the single flush handle assembly that includes flush handle 47, knob 48, and flush lever 45.

FIG. 2 shows the first embodiment of the mounting structure, designated as mounting structure 2, but with vertical bar 4 purposely removed to reveal openings 12 and 13, and FIG. 12 shows the entire mounting structure 2 including vertical bar 4. FIG. 3 is a section view of mounting structure 2 at a cutting plane line A-A in FIG. 2. Mounting structure 2 comprises a main body 64 (FIG. 3), vertical bar 4, and external parts integrally attached to main body 64, including an upper horizontal extension 15 with an opening 12, a lower horizontal extension 16 with an opening 13 located vertically below opening 12, an L-shaped vertical block 17, a protruding section 11 inserted with a hand-tightening nut 6, and a refill tube holder 8 on top. Main body 64 of mounting structure 2 in FIG. 3 has a double-wall cylindrical structure, including an outer cylindrical wall 10, a shorter inner cylindrical wall 18, a ring-shaped horizontal wall 20 integrally attached to the top of outer cylindrical wall 10 and inner cylindrical wall 18, an in-between gap 19 between inner cylindrical wall 18 and outer cylindrical wall 10 and sealed on the top by ring-shaped horizontal wall 20, a top circular opening 14 enclosed by inner cylindrical wall 18, and a larger bottom circular opening 21 enclosed by outer cylindrical wall 10. Outer cylindrical wall 10 of mounting structure 2 has an inside diameter slightly larger than the outside diameter of overflow tube 36 (FIG. 1), and inner cylindrical wall 18 has an outside diameter slightly smaller than the inside diameter of overflow tube 36. Mounting structure 2 is attached to overflow tube 36 by inserting the upper section of the overflow tube inside ring-shaped gap 19 until mounting structure 2 firmly rests on the top of overflow tube 36, and nut 6 is tightened to fasten mounting structure 2 to overflow tube 36, after rotating mounting structure 2 around overflow tube 36 to a proper horizontal or azimuthal location to provide a good contact with flapper valve 37 (FIG. 1). There is a top notch 7 on main body 64 (i.e., the double-wall cylindrical structure) of mounting structure 2, formed by removing a small piece of outer cylindrical wall 10 and an adjacent piece of top horizontal wall 20 to expose inner wall 18 and gap 19. After installing mounting structure 2 over the overflow tube, top notch 7 will expose the top of the overflow tube for the installer to make sure that mounting structure 2 firmly rests on the top of the overflow tube before tightening nut 6. In addition, notch 7 will allow the installer to optionally attach the refill tube to the exposed top of the overflow tube using a commercially available metal or plastic clip; this provision is needed for other embodiments of the mounting structure without the refill tube holder. Mounting structure 2 excluding hand-tightening nut 6 and vertical bar 4 is preferable to be built as a unit.

FIG. 4 is a limited top view of mounting structure 2 in FIG. 2 showing only the outer cylindrical wall 10 with upper horizontal extension 15 in the upper figure and with lower horizontal extension 16 in the lower figure, where a dotted curve shows a part or surface hidden below another part. Opening 13 is vertically below opening 12 to allow vertical bar 4 in FIGS. 8-11 to be inserted into these two openings as shown in FIG. 12. FIG. 5 is a section view of the lower portion of mounting structure 2 at a cutting plane line B-B in FIG. 2; a threaded hole 59 in protruding section 11 is inserted with hand-tightening nut 6 (for fastening mounting structure 2 to the overflow tube), and L-shaped vertical block 17 is externally connected to outer cylindrical wall 10. It should be pointed out that FIG. 5 is also a section view for other embodiments of the mounting structure, including mounting structure 2A at a cutting plane line B-B in FIG. 13, mounting structure 2B at a cutting plane line B-B in FIG. 14, and mounting structure 2C at a cutting plane line B-B in FIG. 17. And, L-shaped vertical block 17 is also part of mounting structure 2D and externally connected to a partial cylindrical wall 10D in FIG. 20.

FIG. 6 is a top view of the upper portion of mounting structure 2, located above L-shaped vertical block 17 in FIG. 2, and FIG. 7 is a side elevation view of refill tube holder 8 in FIG. 2, where dotted lines indicate a hidden circular hole 9 not directly visible. Refill tube holder 8 has a base 22 connected to the top of mounting structure 2 and a circular hole 9 to allow insertion of the refill tube to keep it above the top of circular opening 14 and overflow tube 36 (FIG. 1). The diameter of circular hole 9 is properly sized to ensure the refill tube is tightly inserted inside. It is worth noting that the refill tube is not part of dual flush device 1 and the another end of the refill tube is connected to a small nozzle on the tank inlet valve or the fill valve, purposely omitted in FIG. 1 as previously stated.

FIGS. 8-11 show an embodiment of vertical bar 4 that is part of the mounting structure. FIG. 8 shows a perspective view of an embodiment of vertical bar 4, comprising a top head 33, a short upper section 34 below top head 33, and a vertical body 35 below short upper section 34. FIG. 9 is a section view of top head 33 at a cutting plane line C-C in FIG. 8, and FIG. 10 is a section view of short upper section 34 at a cutting plane line D-D in FIG. 8. FIG. 11 is a section view of vertical body 35 of vertical bar 4 at a cutting plane line E-E in FIG. 8, which has a smooth shape for float 3 to slide along (FIG. 1). Note that opening 12 and opening 13 of mounting structure 2 in FIG. 2 or FIG. 4 have approximately the same shape and size as short upper section 34 and vertical body 35 of vertical bar 4 respectively; they are sized to anchor and hold vertical bar 4 in place in FIG. 12. Furthermore, other shapes and sizes of vertical bar 4 than those shown in FIGS. 8-11 may also be used as long as openings 12 and 13 on the mounting structure are shaped and sized accordingly to properly engage vertical bar 4.

FIG. 13 shows the second embodiment of the mounting structure, designated as mounting structure 2A, which is almost identical to mounting structure 2 (FIG. 12) except having no refill tube holder on top. Previous descriptions of mounting structure 2 except refill tube holder 8 are equally applicable to mounting structure 2A. For example, FIG. 3 is also a section view of mounting structure 2A at a cutting plane line A-A in FIG. 13. As stated earlier, the refill tube can be clipped to the top of the overflow tube exposed by top notch 7 using a metal or plastic clip.

FIG. 14 shows a perspective view of the third embodiment of the mounting structure, designated as mounting structure 2B, and FIG. 15 shows a section view of mounting structure 2B at a cutting plane line A-A in FIG. 14. Similar to mounting structures 2 and 2A, mounting structure 2B comprises a main body 65 (FIG. 15), vertical bar 4, and external parts integrally attached to main body 65, including an upper horizontal extension 15 with an opening 12, a lower horizontal extension 16 with an opening 13 located vertically below opening 12, an L-shaped vertical block 17, and a protruding section 11 inserted with a hand-tightening nut 6. Unlike mounting structures 2 and 2A, main body 65 of mounting structure 2B is a hollow cylinder with a circular central opening 21 enclosed by a cylindrical wall 10, shown in a section view in FIG. 15. Mounting structure 2B has a top notch 7B on main body 65 (FIG. 14), formed by removing a small piece of cylindrical wall 10 to expose any parts behind. Cylindrical wall 10 of mounting structure 2B has an inside diameter slightly larger than the outside diameter of the overflow tube, and it is attached to the overflow tube by sliding over overflow tube 36 and supported at the bottom by a clamp-like device or an elastic compression ring 54 fastened to the overflow tube at a proper axial location in FIG. 16. Mounting structure 2B is fastened to overflow tube 36 at a proper horizontal location above flapper valve 37 by tightening nut 6 (FIG. 16). A top surface of overflow tube 36 is exposed by top notch 7B to provide a place to attach the refill tube using a commercially available metal or plastic clip. Since FIG. 16 contains several parts similar to those in FIG. 1 (e.g., overflow tube 36 and flapper valve 37), they are identified with the same part numbers as in FIG. 1 and have the same descriptions as previously discussed. It is worth noting that FIG. 1 shows entire dual flush device 1 comprising mounting structure 2 and float 3, and FIG. 16 shows mounting structure 2B without Float 3 installed.

FIG. 17 shows a perspective view of the fourth embodiment of the mounting structure, designated as mounting structure 2C, and FIG. 18 shows a section view of mounting structure 2C at a cutting plane line A-A in FIG. 17. Similar to mounting structures 2 and 2A, mounting structure 2C comprises a main body 66 (FIG. 18), vertical bar 4, and external parts integrally attached to main body 66, including an upper horizontal extension 15 including an opening 12, a lower horizontal extension 16 including an opening 13 located vertically below opening 12, an L-shaped vertical block 17, and a protruding section 11 inserted with a hand-tightening nut 6. Unlike mounting structures 2 and 2A, main body 66 of mounting structure 2C is a single-wall cylindrical structure that comprises a cylindrical wall 10 integrally attached at the top to a ring-shaped horizontal wall 20C, which has the same outside diameter but a somewhat smaller inside diameter in comparison to cylindrical wall 10. FIG. 18 shows that cylindrical wall 10 has a circular central opening 21 and ring-shaped horizontal wall 20C has a smaller circular central opening 14C. Cylindrical wall 10 has an inside diameter slightly larger than the outside diameter of the overflow tube and ring-shaped horizontal wall 20C has an inside diameter somewhat smaller than the inside diameter of the overflow tube. Mounting structure 2C has a top notch 7C on main body 66 in FIG. 17 by removing a small piece of cylindrical wall 10 and an adjacent piece of ring-shaped top horizontal wall 20C to expose any parts behind (e.g., to expose a small surface on the overflow tube to provide a place to fasten the refill tube to the top of the overflow tube using a commercially available metal or plastic clip, after attaching mounting structure 2C to the overflow tube). The fourth embodiment of the mounting structure is attached to the overflow tube by placing the single-wall cylindrical structure over the overflow tube and inserting a top section of the overflow tube inside the single-wall cylindrical structure until the ring-shaped top horizontal wall firmly rests on a top of said overflow tube, and nut 6 is tightened to fasten mounting structure 2C to the overflow tube at a proper horizontal location above the flapper valve (FIG. 1).

FIGS. 19-21 shows the features of an adapter 55 and the fifth embodiment of the mounting structure, designated as mounting structure 2D. FIG. 19 shows adapter 55 for attaching and fastening mounting structure 2D to the overflow tube, comprising a clamp 56 with a tightening screw 60 and a built-in external vertical key 57. FIG. 20 is a perspective view of mounting structure 2D, and FIG. 21 is a horizontal section view of mounting structure 2D at a cutting plane line F-F in FIG. 20. Mounting structure 2D comprises a main body 67 formed by a partial cylindrical structure wall 10D with a vertical keyhole 58 inside and a top wall 63 to cover the top of partial cylindrical structure wall 10D (FIGS. 20-21), vertical bar 4, and external parts integrally attached to main body 67, including an upper horizontal extension 15D with an opening 12, a lower horizontal extension 16D with an opening 13 in vertical alignment with opening 12 on upper horizontal extension 15D, and an L-shaped vertical block 17 extending from the bottom of main body 67 to a height below top wall 63 of main body 67. Vertical keyhole 58 (shown in dotted lines in FIG. 20) extends vertically from the bottom of main body 67 of mounting structure 2D to an underside of top wall 63 of main body 67. Vertical keyhole 58 is sized to engage and be tightly inserted with vertical key 57 of adapter 55 (FIG. 19) and it has the same vertical length as vertical key 57. Mounting structure 2D and adapter 55 are configured to be attached and fastened anywhere appropriate to the overflow tube.

Mounting structure 2D has parts similar to those in mounting structure 2 (FIG. 12) as previously stated, including L-shaped vertical block 17 and vertical bar 4 inserted into openings 12 and 13. Mounting structure 2D also has parts partially similar to those in mounting structure 2, including upper horizontal extension 15D with opening 12, lower horizontal extension 16D with opening 13, and partial cylindrical structure wall 10D.

FIGS. 22-29 show various parts of float 3 (FIG. 1). FIG. 22 is a perspective view of an embodiment of float 3, comprising a watertight container 24 with a sealed top cover or top wall 23 and an external bottom part 5 attached to container 24. Container 24 includes all watertight walls to provide buoyancy in water, an external horizontal extension 25 with an opening 26, and an external vertical channel 27 enclosed by inner wall 28 and outer wall 29 on the opposite side. Vertical channel 27 of float 3 is configured to mate and engage L-shaped vertical block 17 of mounting structure 2 (FIG. 12), mounting structure 2A (FIG. 13), mounting structure 2B (FIG. 14), mounting structure 2C (FIG. 17), or mounting structure 2D (FIG. 20). Opening 26 on float 3 in FIG. 22 will be inserted with vertical bar 4 of the mounting structure as shown in FIGS. 1 and 16 and it has a similar shape and a somewhat larger size than vertical body 35 of vertical bar 4 (FIGS. 8 and 11). FIG. 23 is a perspective view of container 24 in FIG. 22 but with top cover 23 and bottom part 5 removed to reveal a vertical block 30 inside container 24, which has a sealed top wall 62 and a threaded hole 52 hidden below sealed top wall 62 (shown in a circular dotted line). FIGS. 24 and 25 are respectively a top view and a bottom view of the portion of container 24 in FIG. 23, where hidden lines show the parts hidden behind another part. Threaded hole 52 inside block 30 begins at an underside of a bottom wall 61 of container 24 and extends upward to an underside of sealed top wall 62 of vertical block 30 (FIGS. 23-25). Vertical block 30 is integrally built with the walls of container 24 as a unit using watertight materials to prevent water seeping into container 24 through threaded hole 52. FIG. 24 shows optional weights 53 placed on bottom wall 61 of container 24 to increase the float weight and enhance stability of float 3 in water; alternatively, another embodiment of the float can be configured to have those weights integrally built into the container walls and/or bottom part 5 of float 3 (FIG. 22) to increase the float weight and enhance float stability in water. It is worth noting that FIG. 25 only shows vertical block 30 in dotted lines as a hidden part above bottom wall 61 of container 24, by disregarding other hidden parts such as optional weights 53 and inner surfaces of container walls.

FIGS. 26 and 27 show respectively a perspective view and a top view of an embodiment of the bottom part of the float, designated as bottom part 5. Bottom part 5 comprises a vertical threaded rod or screw 31 integrally attached to a horizontally elongate bottom head 32, with the vertical axis of threaded rod 31 intersecting the symmetric line of elongate bottom head 32 at the right angle. Bottom part 5 in FIG. 26 is shown in the orientation to be screwed into threaded hole 52 in container 24 of the float (FIGS. 23-25) to become a part of float 3 (FIG. 22). FIGS. 28 and 29 show respectively a perspective view and a top view of another embodiment of the bottom part of the float, designated as bottom part 5A. Bottom part 5A comprises a vertical threaded rod or screw 31A integrally attached to a bent elongate bottom head 32A, with the vertical axis of threaded rod 31A intersecting the symmetric line of bent elongate bottom head 32A at the right angle. Bent elongate bottom head 32A is shaped to have multiple bends (e.g., a bend around the intersected vertical axis of threaded rod 31A and another bend near the tip of bottom head 32A). Bottom part 5A can be screwed into threaded hole 52 of container 24 (FIGS. 23-25) to replace bottom part 5 in FIG. 22 to form another embodiment of the float. It should be noted that FIG. 22 shows the correct horizontal position of bottom part 5 after being screwed into threaded hole 52 of the float.

The vertical length of the float is adjustable because bottom part 5 or 5A does not have to be fully screwed into threaded hole 52 of container 24 of the float. As a result, the vertical length of the float can be either increased by rotating bottom part 5 or 5A away from container 24 or decreased by rotating bottom part 5 or 5A toward container 24. It is important to note that increasing the vertical length of the float will generally use less volume of water in the partial flush by closing the flapper valve earlier, and decreasing the vertical length of the float will generally use more volume of water in the partial flush by closing the flapper valve later. Consequently, the length-adjustable float enables the user to preselect a wide range of water usage in the partial flush from removing liquid wastes to removing a fair load of solid wastes, and this is a great feature of the dual flush device of the present invention.

The dual flush device can be easily installed in the toilet tank in three steps without changing the modular design of the conventional toilets, using mounting structure 2 (FIG. 12) and float 3 (FIG. 22) as an example: (1) removing vertical bar 4 from mounting structure 2 and loosening nut 6, placing the double-wall cylindrical structure of mounting structure 2 (FIG. 3) on the top of the overflow tube (FIG. 1), and lowering it to insert the overflow tube wall inside annular gap 19 until the mounting structure firmly rests on the top of the overflow tube; (2) making sure bottom part 5 of float 3 at the exact horizontal position in FIG. 22, mating vertical channel 27 of the float with L-shaped vertical block 17 of the mounting structure, and then firmly inserting vertical 4 into top opening 12 on the mounting structure, opening 26 on the float, and bottom opening 13 on the mounting structure; and (3) selecting a proper horizontal location of the assembled dual flush device to ensure that bottom part 5 of the float will properly contact the flapper valve (FIG. 1) in the partial flush, before tightening nut 6 to fasten the dual flush device to the overflow tube. After the installation, depress the flush handle to initiate the partial flush to make sure that float 3 will move vertically downward following falling water level in the tank to prematurely close the flapper valve and it will move vertically upward following rising water level during tank refill. It is evident that the vertical movement of external horizontal extension 25 of float 3 along vertical bar 4 and L-shaped vertical block 17 is allowed only within the vertical space between upper horizontal extension 15 and lower horizontal extension 16 of the mounting structure (FIG. 12). In other words, the vertical movement of the float is limited by the mounting structure. Furthermore, the full flush is activated by holding down flush handle briefly to keep the float in place during tank draining.

In summary, the dual flush device of the present invention comprises the mounting structure with five embodiments described and the float with two embodiments discussed. The dual flush device is properly designed to lead to smooth sliding of the float along vertical bar 4 and L-shaped vertical block 17 of the mounting structure in a toilet flush. It is important to note that the dual flush device of the present invention is not limited to the aforementioned embodiments of the mounting structure and the float described in this specification and drawings provided, and it encompasses any and all embodiments within the scope of the invention defined in the claims. 

What is claimed is:
 1. A dual flush device for toilets, the dual flush device comprising: a mounting structure configured to attach and fasten to an overflow tube in a toilet tank; a float connected to said mounting structure through a vertical bar of said mounting structure; wherein said float is configured to move vertically downward following a falling water level in the tank to prematurely close a flapper valve in a partial flush using less volume of water than in a full flush; wherein said float is configured to move vertically upward following a rising water level during tank refill; wherein said dual flush device is configured to work with a single flush handle assembly and said flapper valve; whereby said dual flush device maintains a modular design of conventional toilets to keep the inherent convenience and economy of maintenance and part replacement.
 2. The dual flush device of claim 1, wherein said mounting structure comprises a main body, said vertical bar, and external parts integrally attached to said main body, including an upper horizontal extension with an opening configured to be inserted with said vertical bar, a lower horizontal extension with an opening in vertical alignment with said opening on said upper horizontal extension and configured to be inserted with said vertical bar, an L-shaped vertical block extending from a bottom of said main body to a height below a top surface of said main body, and a protruding section with a threaded hole inserted with a hand-tightening nut, wherein said opening on said upper horizontal extension and said opening on said lower horizontal extension are sized to tightly fit and hold said vertical bar in place, and wherein said upper horizontal extension and said lower horizontal extension of said mounting structure limit the vertical movement of said float.
 3. The dual flush device of claim 2, wherein each of a first embodiment of said mounting structure and a second embodiment of said mounting structure has the main body of a double-wall cylindrical structure that has an outer cylindrical wall and a shorter inner cylindrical wall with an in-between gap, wherein said outer cylindrical wall and said inner cylindrical wall are integrally sealed at a top with a ring-shaped horizontal wall, wherein said outer cylindrical wall has an inside diameter slightly larger than an outside diameter of said overflow tube, wherein said inner cylindrical wall has an outside diameter slightly smaller than an inside diameter of said overflow tube, and wherein said double-wall cylindrical structure has a top notch with a small piece of said outer wall and an adjacent piece of the ring-shaped top horizontal wall removed to expose any parts behind.
 4. The dual flush device of claim 3, wherein each of said first embodiment of said mounting structure and said second embodiment of said mounting structure is attached to said overflow tube by placing said double-wall cylindrical structure over said overflow tube and lowering it until a top section of said overflow tube is inserted into said gap between said outer cylindrical wall and said inner cylindrical wall and said double-wall cylindrical structure firmly rests on a top of said overflow tube, and wherein each of said first embodiment of said mounting structure and said second embodiment of said mounting structure is fastened at a proper horizontal location above said flapper valve by tightening said hand-tightening nut of said mounting structure.
 5. The dual flush device of claim 4, wherein said first embodiment of said mounting structure further has a refill tube holder that is integrally attached to a top surface adjacent to a top opening of said double-wall cylindrical structure for fastening a refill tube above said top opening.
 6. The dual flush device of claim 3, wherein a third embodiment of said mounting structure has the main body of a hollow cylinder with a circular central opening at an inside diameter slightly larger than said outside diameter of said overflow tube, wherein said hollow cylinder has a top notch with a small piece of a cylindrical wall removed to expose any parts behind, wherein said third embodiment of said mounting structure is supported at a bottom by a clamp-like device fastened at a proper axial location to said overflow tube, wherein said third embodiment of said mounting structure is attached to said overflow tube by lowering said hollow cylinder of said mounting structure to insert a top section of said overflow tube inside until firmly resting on said clamp-like device, wherein said third embodiment of said mounting structure is fastened to said overflow tube at a proper horizontal location above said flapper valve by tightening said hand-tightening nut of said mounting structure.
 7. The dual flush device of claim 6, wherein a fourth embodiment of said mounting structure has a main body of a single-wall cylindrical structure that comprises a cylindrical wall with a circular central opening integrally attached at a top to a ring-shaped horizontal wall that has a same outside diameter but a somewhat smaller inside diameter in comparison to said cylindrical wall, wherein said cylindrical wall has an inside diameter slightly larger than said outside diameter of said overflow tube and said ring-shaped horizontal wall has an inside diameter somewhat smaller than said inside diameter of said overflow tube, wherein said single-wall cylindrical structure has a top notch by removing a small piece of said cylindrical wall and an adjacent piece of the ring-shaped top horizontal wall to expose any parts behind, wherein said fourth embodiment of said mounting structure is attached to said overflow tube by placing it over said overflow tube and inserting a top section of said overflow tube inside said single-wall cylindrical structure until the ring-shaped top horizontal wall firmly rests on a top of said overflow tube, and wherein said fourth embodiment of said mounting structure is fastened to said overflow tube at a proper horizontal location above said flapper valve by tightening said hand-tightening nut of said mounting structure.
 8. The dual flush device of claim 7, wherein a fifth embodiment of said mounting structure has a main body of a partial cylindrical structure with a vertical keyhole inside extending from a bottom of said partial cylindrical structure to an underside of a sealed top wall of said partial cylindrical structure, wherein said fifth embodiment of said mounting structure uses an adapter that comprises a clamp for fastening to said overflow tube and a vertical key integrally attached to an outer surface of said clamp, wherein said vertical key of said adapter is configured to tightly fit into said vertical keyhole of said partial cylindrical structure, wherein said adapter is attached and fastened to said overflow tube by sliding said clamp of said adapter around said overflow tube to a proper axial and horizontal location and tightening said clamp, and wherein said fifth embodiment of said mounting structure is attached and fastened to said overflow tube by placing said vertical keyhole of said main body over said vertical key of said adapter and lowering it until said vertical key of said adapter is fully inserted into said keyhole of said partial cylindrical structure.
 9. The dual flush device of claim 2, wherein said float comprises a watertight container with all watertight walls including a sealed top cover to provide buoyancy in water and a bottom part vertically attached to said container, wherein said container includes an external horizontal extension with an opening to be loosely inserted with said vertical bar of said mounting structure, wherein said container further includes an external vertical channel enclosed by two side walls configured to engage said L-shaped vertical block of said mounting structure, wherein an engagement of said vertical channel of said float with said L-shaped vertical block of said mounting structure will place said opening on said external horizontal extension of said float between and in a vertical alignment with said opening on said upper horizontal extension and said opening on said lower horizontal extension of said mounting structure to allow an insertion of said vertical bar into all three openings, wherein the insertion of said vertical bar into the three openings connects said float to said mounting structure to form said dual flush device, wherein said float is configured to slide along said vertical bar and said L-shaped vertical block of said mounting structure in a toilet flush, and wherein said float will move vertically downward with falling water level in the tank in said partial flush and will move vertically upward with rising water level during tank refill.
 10. The dual flush device of claim 9, wherein said container of said float further includes a watertight, internal vertical block and optional weights on a bottom wall, wherein there is a threaded hole inside said internal vertical block extending vertically from a bottom of said container to a location below a sealed top wall of said vertical block, and wherein said optional weights on said bottom wall of said container can be replaced with weights integrally built into the container walls.
 11. The dual flush device of claim 10, wherein an embodiment of said bottom part of said float comprises a vertical threaded rod integrally attached to an elongate bottom head, wherein said embodiment of said bottom part is configured to be vertically screwed into said threaded hole inside said internal vertical block of said container, and wherein an embodiment of said float comprises said container and said embodiment of said bottom part screwed into said container.
 12. The dual flush device of claim 11, wherein another embodiment of said bottom part of said float comprises a vertical threaded rod integrally attached to a bent elongate bottom head with multiple bends, wherein said another embodiment of said bottom part is configured to be vertically screwed into said threaded hole inside said internal vertical block of said container, and wherein another embodiment of said float comprises said container and said another embodiment of said bottom part screwed into said container.
 13. The dual flush device of claim 12, wherein a vertical length of said float is adjustable by varying an insertion length of said bottom part into said threaded hole inside the float container, wherein said vertical length of said float is increased by rotating said bottom part away from said container and is decreased by rotating said bottom part toward said container, wherein an increase in said vertical length of said float will in general prematurely close said flapper valve earlier to lead to less volume of water used in said partial flush, wherein a decrease in said vertical length of said float will in general prematurely close said flapper valve later to lead to more volume of water used in said partial flush, and wherein the length-adjustable float of said dual flush device enables a user to preselect a wide range of water usage in said partial flush from removing liquid wastes to removing a fair load of solid wastes.
 14. A dual flush device for toilets, the dual flush device comprising: a mounting structure including a main body, a vertical bar, and external parts integrally attached to said main body; and a float including a watertight container with a sealed top cover, an external horizontal extension with an opening integrally attached to an outer wall of said container, an external vertical channel enclosed by two side walls of said container, and a bottom part inserted into said container; wherein said external parts of said mounting structure include an upper horizontal extension with an opening, a lower horizontal extension with an opening vertically below said opening on said upper horizontal extension, an L-shaped vertical block, and a protruding section with a threaded hole inside to fit a hand-tightening nut; wherein said external vertical channel of said float is configured to engage said L-shaped vertical block of said mounting structure and the engagement is configured to position said opening on said external horizontal extension of said float vertically between and in alignment with said opening on said upper horizontal extension and said opening on said lower horizontal extension of said mounting structure; wherein said float is connected to said mounting structure by sequentially inserting said vertical bar into said opening on said upper horizontal extension of said mounting structure, said opening on said external horizontal extension of said float, and said opening on said lower horizontal extension of said mounting structure; wherein said float is configured to move vertically downward along said vertical bar and said L-shaped vertical block of said mounting structure following falling water level in a toilet tank in a partial flush; wherein said float is configured to move vertically upward along said vertical bar and said L-shaped vertical block of said mounting structure following rising water level during tank refill; wherein vertical movement of said float is limited by said mounting structure; wherein said mounting structure is configured to attach and fasten to an overflow tube in a toilet tank; wherein said dual flush device is configured to operate with a conventional single flush handle assembly and a flapper valve in the tank; whereby said dual flush device maintains a modular design of conventional toilets to keep the inherent convenience and economy of maintenance and part replacement.
 15. The dual flush device of claim 14, wherein an embodiment of said mounting structure has the main body of a double-wall cylindrical structure that has an outer cylindrical wall and a shorter inner cylindrical wall with an in-between gap, wherein said outer cylindrical wall and said inner cylindrical wall are integrally sealed at a top with a ring-shaped horizontal wall, wherein said double-wall cylindrical structure has a top notch by removing a small piece of said outer cylindrical wall and a small piece of the adjacent top horizontal wall to expose any parts behind, wherein said outer cylindrical wall has an inside diameter slightly larger than an outside diameter of said overflow tube, wherein said inner cylindrical wall has an outside diameter slightly smaller than an inside diameter of said overflow tube, wherein said mounting structure further includes a refill tube holder integrally attached to a top surface of said double-wall cylindrical structure for fastening a refill tube above a top opening, wherein said mounting structure is attached to said overflow tube by placing said in-between gap of said double-wall cylindrical structure over said overflow tube and lowering said mounting structure until it firmly rests on a top of said overflow tube, and wherein said mounting structure is fastened to said overflow tube at a proper horizontal location above said flapper valve by tightening said hand-tightening nut.
 16. The dual flush device of claim 15, wherein another embodiment of said mounting structure has the main body of a hollow cylinder with a circular central opening at an inside diameter slightly larger than said outside diameter of said overflow tube, wherein said hollow cylinder has a top notch by removing a small piece of a cylindrical wall to expose any parts behind, wherein a clamp-like device is fastened to said overflow tube at a proper axial location for supporting said mounting structure, wherein said mounting structure is attached to said overflow tube by sliding said hollow cylinder over said overflow tube until it firmly rests on said clamp-like device, and wherein said mounting structure is fastened to said overflow tube at a proper horizontal location above said flapper valve by tightening said hand-tightening nut.
 17. The dual flush device of claim 16, wherein a further embodiment of said mounting structure has the main body of a single-wall cylindrical structure integrally attached at a top to a ring-shaped top horizontal wall that has a same outside diameter but a smaller inside diameter compared to said single-wall cylindrical structure, wherein said single-wall cylindrical structure has an inside diameter slightly larger than said outside diameter of said overflow tube, wherein said ring-shaped top horizontal wall has an inside diameter somewhat smaller than said inside diameter of said overflow tube, wherein said single-wall cylindrical structure has a top notch by removing a small piece of the cylindrical wall and an adjacent piece of said ring-shaped top horizontal wall to expose any parts behind, wherein said mounting structure is attached to said overflow tube by sliding said single-wall cylindrical structure over said overflow tube until said ring-shaped top horizontal wall firmly rests on a top of said overflow tube, and wherein said mounting structure is fastened to said overflow tube by tightening said hand-tightening nut after setting said mounting structure at a proper horizontal location above said flapper valve.
 18. The dual flush device of claim 14, wherein said container of said float contains a watertight, internal vertical block with a sealed top wall and optional weights, wherein said internal vertical block has a threaded hole inside that extends vertically from an underside of a bottom wall of said container to an underside of said sealed top wall, wherein an embodiment of said bottom part of said float comprises a vertical threaded rod integrally attached to an elongate bottom head, wherein another embodiment of said bottom part comprises a vertical threaded rod integrally attached to a bent elongate bottom head with multiple horizontal bends, wherein each embodiment of said bottom part is configured to screw into said threaded hole inside said internal vertical block of said container, and wherein said optional weights inside said container can be integrally built into container walls.
 19. The dual flush device of claim 18, wherein a vertical length of said float is adjustable, wherein said vertical length can be increased by rotating said bottom part away from said container or decreased by rotating said bottom part toward said container, wherein said vertical length of said float influences a volume of water used in said partial flush, wherein a longer vertical length of said float will generally provide less volume of water in said partial flush by prematurely closing said flapper valve earlier, wherein a shorter vertical length of said float will generally provide more volume of water in said partial flush by prematurely closing said flapper valve later, and wherein the length-adjustable float of said dual flush device will enable a user to preselect a wide range of water usage in said partial flush from removing liquid wastes to removing a fair load of solid wastes. 